Arc suppressing means



Jan. 25, 1944. A. HUFNAGEL ARC SUPPRESSING MEANS Filed June 23, 1942 JilPatented Jan. 25, 1944 ARC SUPPRESSING MEANS Andrew Hufnagel,Wilkinsburg, Pa., assignor to The Union Switch & Signal Company,Swissvaie, Pa... a corporation of Pennsylvania Application June 23,1942, Serial No. 448,175

1 Claim.

My invention relates to improved means for reducing the arcing whichoccurs at a contact which controls the circuit of an inductive winding.

In some types of apparatus a transformer is employed which has a primarywinding having an intermediate terminal connected to a source ofunidirectional current, while movable contacts cooperate with stationarycontacts to alternately connect the other terminal of the source ofcurrent to the end terminals of the transformer primary winding.

On interruption of the supply of energy to either portion of thetransformer primary winding there is an are between the stationary andmovable contacts which erodes these contacts and reduces their life.

It is an object of this invention to provide improved means for reducingthe are which occurs between the contacts of apparatus of the typedescribed.

A further object of the invention is to provide means for reducing thevoltage induced in each ortion of the primary winding of a transformeron interruption of the supply of energy to this winding portion, andthus reduce the are which occurs at the contacts'which control thesupply of energy to this winding portion.

Another object of the invention is to provide improved arc suppressingmeans.

I shall describe one form of apparatus embodying my invention, and shallthen point out the novel features thereof in claim.

In the drawing the single figure is a diagram illustrating one form ofapparatus embodying my invention.

In practicing my invention I connect between each end terminal of thetransformer primary winding and a terminal of the battery or source ofcurrent an asymmetric unit poled to permit flow of energy of thepolarity opposite to that supplied from the battery to that portion ofthe transformer primary winding. These asymmetric units cause eachportion of the transformer primary winding to act as a snubbing windingon interruption of the supply of energy to the other portion of thetransformer primary winding to thereby retard the collapse of the fluxin the transformer core and correspondingly reduce the are caused by thevoltage induced in said other portion of the transformer primary windingby the collapse of this flux. 7

Referring to the drawing, there is shown therein a code following relayOR, a transformer T. and a code detecting relay H. Coded energyconsisting of energy impulses separated by nonenergy periods is suppliedto the relay CR. One terminal of a battery or other source ofunidirectional current is connected to an intermediate terminal of theprimary winding of transformer T, while when the relay OR is releasedits contact I 0 connects the other terminal of the battery to the lowerend terminal of the transformer primary winding. On the supply of animpulse of energy to the relay CR its contacts pick up and contact Ininterrupts connection from the battery to the lower end terminal of thetransformer primary winding and connects the battery to the upper endterminal of the transformer primary winding. Similarly, on interruptionof the supply of energy to the relay CR its contacts release and contactill interrupts connection from the battery to the upper end terminal ofthe transformer primary winding and connects the battery to the lowerterminal of the transformer primary winding.

When the lower portion of the transformer primary winding is energizedflux of one relative polarity is developed in the transformer core,while when the supply of energy to this portion of the transformerprimary winding is interrupted this flux collapses. On the supply ofenergy to the upper portion of the transformer primary winding flux ofthe other polarity is developed in the transformer core, while any fluxremaining in the core from energization of the lower portion of thetransformer primary winding is utilized in the energization of relay H.

As a result of changes in the flux in the core of the transformer energyis induced in the secondary winding of the transformer from which it issupplied to the relay H. The energy supplied to the relay H is rectifiedby contact ll of relay GR in the manner explained in Letters Patent ofthe United States No. 2,237,788, granted to Frank H. Nicholson andLeslie R. Allison on April 8, 1941.

On movement of the contact ill away from either of its positions withconsequent interruption of the supply of energy to a portion of thetransformer primary winding the flux in the transformer core collapsesand induces a voltage in each portion of the transformer primarywinding. The voltage induced in the portion of the winding, the circuitof which has been interrupted, creates an are at the contacts whichcontrol the circuit of this winding portion, and this invention providesmeans to reduce this are.

An asymmetric unit i4 is connected between the upper end terminal of thetransformer primary winding and the terminal of the battery which isconnected to the movable contact ID. This asymmetric unit is poled toprevent flow of energy through the unit from the battery to the upperportion of the transformer primary winding.

Similarly, an asymmetric unit II is connected/c ing with the result thatthe flux in the trans former core diminishes and causes a voltage to beinduced in both portions of the transformer primary winding. Thepolarity of the voltage induced in the lower portion of the transformerprimary winding is such that current will freely flow through therectifier l5. Accordingly, the lower portion of the transformer primarywinding is short circuited through the asymmetric unit I5 and thebattery, and this short circuited winding retards the collapse of theflux in the transformer core with the result that the voltage of theenergy impulse induced in the upper portion of the primary winding ismuch lower than it otherwise would be, while the are which occurs at thecontact in the circuit of the upper portion of the transformer primarywinding is correspondingly diminished in magnitude.

Similarly, when the contact l0 picks up after it has been in itsreleased position, the supply of energy to the lower portion of thetransformer primary winding is interrupted and the flux in thetransformer core collapses and a voltage is induced in each portion ofthe transformer primary winding. The voltage induced in the upperportion of the transformer primary winding is of such polarity thatcurrent will flow through the asymmetric unit l4 so the upper portion ofthe transformer primary winding is short circuited through theasymmetric unit I! and the battery. This short circuited winding delaysthe collapse of flux in the transformer core and thus reduces thevoltage of the energy induced in the lower portion of the transformerprimary winding with the result that the are developed at the contactwhich controls the supply of energy to the lower portion of thetransformer primary winding is much smaller than it otherwise would be.

The internal resistance of the battery is relatively low, while theresistance of the asymmetric units to flow of current in the forwarddirection is also relatively low. Accordingly, the snubbing circuits forthe transformer primary winding portions are of low resistance and thesewindings effectively retard collapse of the flux in the transformercore.

The asymmetric units I 4 and ii are incorporated in the circuits in suchmanner that they do not interfere with the operation of the equip ment.

On movement of contact I 0 to its picked-up position and the consequentsupply of energy to the upper portion of the primary winding-of thetransformer. an impulse of voltage is induced in the lower portion ofthe transformer primary winding. However, this voltage is of theopposite polarity to that induced in this portion of the winding oninterruption of the supply of energy to the upper portion of thetransformer primary winding and is of the wrong polarity for current toflow through the asymmetric unit It. Accordingly, the lower portion ofthe transformer primary winding does not function as a short circuitedor snubbing winding at this time and does not divert energy from thetransformer secondary winding;

Similarly, on movement of contact Hi to its released position to supplyenergy to the lower portion of the transformer primary winding, animpulse of voltage is induced in the upper portion of this winding, butthis voltage is of the wrong polarity for current to flow through theasymmetric unit M.

It will be seen, therefore, that the asymmetric units provided by thisinvention operate to retard or delay the collapse of the flux in thetransformer core on interruption of the supply of energy to eitherportion of the transformer primary winding, and thus reduce the arcingwhich occurs at the contacts which control the supply of energy to thetransformer primary windings.

Although the invention has been illustrated and described in connectionwith decoding apparatus of the type employed in railway signalingsystems, the invention is not limited to use in this manner but isadapted for use in other situations, as, for example, to reduce thearcing at the contacts of tuned alternators or of B-battery eliminatorsfor use in radio sets.

Although I have herein illustrated and described only one form ofapparatus embodying my invention, it is understood that various changesand modifications may be made therein within the scope of the appendedclaim without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

In combination with an inductive winding having an intermediate terminalconnected to one terminal of a source of unidirectional current andhaving associated therewith alternately closed first and secondcontacts, said first contact being effective when closed to connect thefirst end terminal of said winding to the other terminal of said source,said second contact being effective when closed to connect the secondend terminal of said winding to the other terminal of said source, aresuppressing means comprising a first asymmetric unit connected betweenthe first end terminal of said winding and said other terminal of saidsource and a second asymmetric unit connected between the second endterminal of said winding and said other terminal of said source, each ofsaid asymmetric units being poled to prevent flow of energy therethroughfrom the battery to the associated portion of said winding.

ANDREW HUFNAGEL.

